N/A
The invention generally relates to micellar systems for use in biologic systems. More particularly, a process is provided for the use of reverse micelles for the delivery of nucleic acids and genes to cells.
Biologically active compounds such as proteins, enzymes, and nucleic acids have been delivered to the cells using amphipathic compounds that contain both hydrophobic and hydrophilic domains. Typically these amphipathic compounds are organized into vesicular structures such as liposomes, micellar, or inverse micellar structures. Liposomes can contain an aqueous volume that is entirely enclosed by a membrane composed of lipid molecules (usually phospholipids) (R.C. New, p. 1, chapter 1, xe2x80x9cIntroductionxe2x80x9d in Liposomes: A Practical Approach, ed. R.C. New IRL Press at Oxford University Press, Oxford, 1990). Micelles and inverse micelles are microscopic vesicles that contain amphipathic molecules but do not contain an aqueous volume that is entirely enclosed by a membrane. In micelles the hydrophilic part of the amphipathic compound is on the outside (on the surface of the vesicle) whereas in inverse micelles the hydrophobic part of the amphipathic compound is on the outside. The inverse micelles thus contain a polar core that can solubilize both water and macromolecules within the inverse micelle. As the volume of the core aqueous pool increases the aqueous environment begins to match the physical and chemical characteristics of bulk water. The resulting inverse micelle can be referred to as a microemulsion of water in oil (Schelly, Z. A. Current Opinion in Colloid and Interface Science, 37-41, 1997; Castro, M. J. M., Cabral, J. M. S. Biotech. Adv. 6, 151-167, 1988).
Microemulsions are isotropic, thermodynamically stable solutions in which substantial amounts of two immiscible liquids (water and oil) are brought into a single phase due to a surfactant or mixture of surfactants. The spontaneously formed colloidal particles are globular droplets of the minor solvent, surrounded by a monolayer of surfactant molecules. The spontaneous curvature, HO of the surfactant monolayer at the oil/water interface dictates the phase behavior and microstructure of the vesicle. Hydrophilic surfactants produce oil in water (O/W) microemulsions (H0 greater than 0), whereas lipophilic surfactants produce water in oil (W/O) microemulsions. When the hydrophile-lipophile properties of the surfactant monolayer at the water/oil interface are balanced bicontinuous-type microemulsions are formed (H0=0).
Positively-charged, neutral, and negatively-charged liposomes have been used to deliver nucleic acids to cells. For example, plasmid DNA expression in the liver has been achieved via liposomes delivered by tail vein or intraportal routes. Positively-charged micelles have also been used to package nucleic acids into complexes for the delivery of the nucleic acid to cells. Negatively-charged micelles have been used to condense DNA, however they have not been used for the delivery of nucleic acids to cells (Imre, V. E., Luisi, P. L. Biochemical and Biophysical Research Communications, 107, 538-545, 1982). This is because the previous efforts relied upon the positive-charge of the micelles to provide a cross-bridge between the polyanionic nucleic acids and the polyanionic surfaces of the cells. Micelles that are not positively-charged, or that do not form a positively charged complex cannot perform this function. For example, a recent report demonstrated the use of a cationic detergent to compact DNA, resulting in the formation of a stable, negatively-charged particle (Blessing, T., Remy, J. S., Behr, J. P. Proc. Natl. Acad. Sci. USA, 95, 1427-1431, 1998). A cationic detergent containing a free thiol was utilized which allowed for an oxidative dimerization of the surfactant to the disulfide in the presence of DNA. However, as expected, the negatively-charged complex was not effective for transfection. Reverse (water in oil) micelles has also been used to make cell-like compartments for molecular evolution of nucleic acids (Tawfik, D. S. and Griffiths, A.D. Nature Biotechnology 16:652, 1998). Cleavable micellar systems was not used in this system.
In addition, Wolff et al. have developed a method for the preparation of DNA/amphipathic complexes including micelles in which at least one amphipathic compound layer that surrounds a non-aqueous core that contains a polyion such as a nucleic acid (Wolff, J., Budker, V., and Gurevich, V. U.S. Pat. No. 5,635,487).
Cleavable Micelles
A new area in micelle technology involves the use of cleavable surfactants to form the micelle. Surfactants containing an acetal linkage, azo-containing surfactants, elimination of an ammonium salt, quaternary hydrazonium surfactants, 2-alkoxy-N,N-dimethylamine N-oxides, and ester containing surfactants such as ester containing quaternary ammonium compounds and esters containing a sugar have been developed.
These cleavable surfactants within micelles are designed to decompose on exposure to strong acid, ultraviolet light, alkali, and heat. These conditions are very harsh and are not compatible with retention of biologic activity of biologic compounds such as proteins or nucleic acids. Thus, biologically active compounds have not been purified using reverse micelles containing cleavable surfactants.
Complexation of Nucleic Acids with Polycations
Polymers are used for drug delivery for a variety of therapeutic purposes. Polymers have also been used for the delivery of nucleic acids (polynucleotides and oligonucleotides) to cells for therapeutic purposes that have been termed gene therapy or anti-sense therapy. One of the several methods of nucleic acid delivery to the cells is the use of DNA-polycation complexes. It was shown that cationic proteins like histones and protamines or synthetic polymers like polylysine, polyarginine, polyornithine, DEAE dextran, polybrene, and polyethylenimine were effective intracellular delivery agents while small polycations like spermine were ineffective. As a result the main mechanism of DNA translocation to the intracellular space might be non-specific adsorptive endocytosis which may be more effective then liquid endocytosis or receptor-mediated endocytosis. Furthermore, polycations are a very convenient linker for attaching specific receptors to DNA and as result, DNA-polycation complexes can be targeted to specific cell types.
There are a variety of molecules (gene transfer enhancing signals) that can be covalently attached to the gene in order to enable or enhance its cellular transport. These include signals that enhance cellular binding to receptors, cytoplasmic transport to the nucleus and nuclear entry or release from endosomes or other intracellular vesicles.
Nuclear localizing signals enhance the entry of the gene into the nucleus or directs the gene into the proximity of the nucleus. Such nuclear transport signals can be a protein or a peptide such as the SV40 large T ag NLS or the nucleoplasmin NLS.
Other molecules include ligands that bind to cellular receptors on the membrane surface increasing contact of the gene with the cell. These can include targeting group such as agents that target to the asialoglycoprotein receptor by using asiologlycoproteins or galactose residues. Other proteins such as insulin, EGF, or transferrin can be used for targeting. Peptides that include the RGD sequence can be used to target many cells. Chemical groups that react with sulfhydryl or disulfide groups on cells can also be used to target many types of cells. Folate and other vitamins can also be used for targeting. Other targeting groups include molecules that interact with membranes such as fatty acids, cholesterol, dansyl compounds, and amphotericin derivatives.
Size of a DNA complex may be a factor for gene delivery in vivo. Many times, the size of DNA that is of interest is large, and one method of delivery utilizes compaction techniques. The DNA complex needs to cross the endothelial barrier and reach the parenchymal cells of interest. The largest endothelia fenestrae (holes in the endothelial barrier) occur in the liver and have average diameter of 100 nm. The trans-epithelial pores in other organs are much smaller, for example, muscle endothelium can be described as a structure which has a large number of small pores with a radius of 4 nm, and a very low number of large pores with a radius of 20-30 nm.(Rippe, B. Physiological Rev, 1994). The size of the DNA complex is also important for the cellular uptake process. After binding to the target cells the DNA complex should be taken up by endocytosis. Since the endocytic vesicles have a homogenous internal diameter of about 100 nm in hepatocytes, and are of similar size in other cell types, the DNA is compacted to be smaller than 100 nm.
Compaction of DNA
There are two major approaches for compacting DNA: 1. Multivalent cations with a charge of three or higher have been shown to condense DNA. These include spermidine, spermine, Co(NH3)63+,Fe3+, and natural or synthetic polymers such as histone H1, protamine, polylysine, and polyethylenimine. One analysis has shown DNA condensation to be favored when 90% or more of the charges along the sugar-phosphate backbone are neutralized (Wilson, R. W., Bloomfield, V. A. Biochemistry 18, 2192-2196, 1979). 2. Polymers (neutral or anionic) which can increase repulsion between DNA and its surroundings have been shown to compact DNA. Most significantly, spontaneous DNA self-assembly and aggregation process have been shown to result from the confinement of large amounts of DNA, due to excluded volume effect (Strzelecka, T. E., Rill, R. L. Biopolymers 30, 803-14, 1990; Strzelecka, T. E., Rill, R. L. Biopolymers 30, 57-71, 1990). Since self-assembly is associated with locally or macroscopically crowded DNA solutions, it is expected, that DNA insertion into small water cavities with a size comparable to the DNA will tend to form mono or oligomolecular compact structures.
Micelles and Reverse Micelles
Reverse micelles (water in oil microemulsions) are widely used as a host for biomolecules. Examples exist of both recovery of extracellular proteins from a culture broth and recovery of intracellular proteins. Although widely used, recovery of the biomolecules is difficult due to the stability of the formed micelle and due to incomplete recovery during the extraction process. Similarly, purification of DNA or other biomolecules from endotoxin and plasma is difficult to accomplish. One common method employing Triton results in incomplete separation of the DNA or biomolecules from the emulsion.
Reverse micelles have been widely used as a host for enzymatic reactions to take place. In many examples, enzymatic activity has been shown to increase with micelles, and has allowed enzymatic reactions to be conducted on water insoluble substrates. Additionally, enzymatic activity of whole cells entrapped in reverse micelles has been investigated (Gajjar, L., Singh, A., Dubey, R. S., Srivastava, R. C. Applied Biochemistry and Biotechnology, 66, 159-172, 1997). The cationic surfactant cetyl pyridinuim chloride was utilized to entrap Baker""s yeast and Brewer""s yeast inside a reverse micelle.
Micelles have also been used as a reaction media. For example, a micelle has been used to study the kinetic and synthetic applications of the dehydrobromination of 2-(p-nitrophenyl) ethyl bromide. Additionally, micelles have found use as an emulsifier for emulsion polymerizations.
Micelles have been utilized for drug delivery. For example, an AB block copolymer has been investigated for the micellar delivery of hydrophobic drugs. Transport and metabolism of thymidine analogues has been investigated via intestinal absorption utilizing a micellar solution of sodium glycocholate. Additionally, several examples of micelle use in transdermal applications have appeared. For example, sucrose laurate has been utilized for topical preparations of cyclosporin A.
The present invention provides for the transfer of polynucleotides, and biologically active compounds into parenchymal cells within tissues in situ and in vivo, utilizing reverse micelles delivered intravasculary, intrarterially, intravenous, orally, intraduodenaly, via the jejunum (or ileum or colon), rectally, transdermally, subcutaneously, intramuscularly, intraperitoneally, intraparenterally, via direct. injections into tissues such as the liver, lung, heart, muscle, spleen, pancreas, brain (including intraventricular), spinal cord, ganglion, lymph nodes, lymphatic system, adipose tissues, thyroid tissue, adrenal glands, kidneys, prostate, blood cells, bone marrow cells, cancer cells, tumors, eye retina, via the bile duct, or via mucosal membranes such as in the mouth, nose, throat, vagina or rectum or into ducts of the salivary or other exocrine glands.
By xe2x80x9cdeliveredxe2x80x9d we mean that the polynucleotide becomes associated with the cell. The polynucleotide can be on the membrane of the cell or inside the cytoplasm, nucleus, or other organelle of the cell. The process of delivering a polynucleotide to a cell has also been commonly termed xe2x80x9ctransfectionxe2x80x9d or the process of xe2x80x9ctransfectingxe2x80x9d and also it has been termed xe2x80x9ctransformationxe2x80x9d. The polynucleotide could be used to produce a change in a cell that can be therapeutic. The delivery of polynucleotides or genetic material for therapeutic purposes is commonly called xe2x80x9cgene therapyxe2x80x9d. The polynucleotides or genetic material being delivered are generally mixed with transfection reagents prior to delivery. A biologically active compound is a compound having the potential to react with biological components. Pharmaceuticals, proteins, peptides, hormones, cytokines, antigens and nucleic acids are examples of biologically active compounds. The reverse micelle may be negatively-charged, zwitterionic, or neutral. Additionally, the present invention provides for the purification of biomolecules by solubilizing the biomolecule into a cleavable reverse micelle and then cleaving the micelle under conditions that will not destroy the biological activity of the biomolecule. These processes can be used for transferring nucleic acids or biomolecules into cells or an organism such as for drug delivery, or may also be used for analytical methods.
The process of utilizing cleavable reverse micelles for the purification of biomolecules has advantages over current methodology. Isolation of the biomolecule will be enhanced by cleaving the reverse micelle. This will separate the polar group from the non-polar group on the surfactant and therefore eliminate the formation of emulsions and therefore simplify the isolation process. Cleavage conditions will be such that the biological activity of the biomolecule is not destroyed. Another advantage of the invention is the use of reverse micelles for gene delivery. The reverse micelle can compact the polynucleotide, a critical step for gene delivery, especially in vivo. The micelle containing the compacted polynucleotide can then be utilized as a reaction vesicle in which additional compounds can be added to the DNA. For example, a polycation could be added to the polynucleotide/reverse micelle solution to form a polycation/polynucleotide complex within the reverse micelle. Additionally, the polynucleotide/reverse micelle system is used as a vesicle for template polymerization of the DNA or caging of the DNA in which the polycation is crosslinked. A variety of chemical reactions can take place with in the vesicle preferably without modifying the nucleic acid. The polynucleotide/reverse micelle system also has advantages in that the micelle may be cleaved under physiological conditions involved along the xe2x80x9ctransfection pathway.xe2x80x9d The surfactant can be altered so that micellular cleavage occurs at different point along this pathway. By xe2x80x9ctransfection pathwayxe2x80x9d we mean any point at which the polynucleotide/reverse micelle system is introduced to a solution (i.e., blood, serum) that contains parenchymal cells, or to the cells (for example the skin or mucousal membranes) through the inclusion of the polynucleotide into the nucleus of the parenchymal cell.
In a preferred embodiment, described is a complex for delivery to a cell, comprising: inserting a nucleic acid into a reverse micelle. A compacting agent may be added to the complex as well as a delivery enhancing ligand or compound.
In a preferred embodiment, a process for delivering a complex to a cell is described, comprising inserting a nucleic acid into a reverse micelle.
In a preferred embodiment, the nucleic acid or biomolecule is solubilized into a reverse micelle with an internal water volume for delivery of the biomolecule to parenchymal cells. A compound can be added to the nucleic acid/micelle mixture. Such compounds include polymers such as polyions (polycations such as spermine, polyamines, polylysine, polyethylimine (PEI), and polyanions), proteins, peptides, enzymes, hydrophobic compounds, and amphipathic compounds (to form a second layer around the micelle). Such compounds include compounds that compact the DNA, provide a cell transfer enhancing ligand or provide another layer to the micelle.
In another preferred embodiment, the nucleic acid or biomolecule is complexed with another molecule prior to micelle formation. For example, a polymer such as polylysine is added to the nucleic acid and then crosslinked to cage the nucleic acid. When a nucleic acid is caged a polymer is formed since the polylysine (or any type of polymer) acts as a monomer that is being included in another polymer.
Another preferred embodiment provides a method of making a compound for delivery to a cell, comprising: adding one or more compounds to the nucleic acid or biomolecule/reverse micelle complex prior to delivery to the cell, thereby providing a deliverable complex. For example, another surfactant or a polyion might be added to the complex. The cell can be a prokaryote or eukaryote and can be a plant, animal or mammalian cell.
Another preferred embodiment provides a method of making a compound for delivery to a cell, comprising: modifying a molecule in the presence of the biomolecule/reverse micelle complex thereby providing a deliverable complex.
In another preferred embodiment, the parenchymal cell is solubilized within a reverse micelle. A reverse micelle containing a polynucleotide would be added to the parenchymal cell containing reverse micelle. After an appropriate amount of time, the parenchymal cell would be purified, and delivered to a mammal.
In another preferred embodiment the biomolecule is solubilized utilizing one of the following procedures.
Procedure 1
a) mixing of the biomolecule into an aqueous solution
b) then mixing the aqueous solution containing the biomolecule with a hydrocarbon or halohydrocarbon containing a surfactant with agitation or sonication
Procedure 2
Mixing of biomolecule into a solution containing a reverse micelle with agitation or sonication.
Procedure 3
a) mixing the biomolecule into an aqueous solution
b) then extracting the aqueous solution containing the biomolecule with a hydrocarbon or halohydrocarbon containing a reverse micelle and separating the phases.
In another preferred embodiment, the biomolecule is purified comprising a step in which a reverse micelle is destroyed.
In another preferred embodiment, the biomolecule can be purified by utilizing one of the following procedures.
Procedure 1
a) mixing of the biomolecule into an aqueous solution
b) then mixing the aqueous solution containing the biomolecule with a hydrocarbon or halohydrocarbon containing a surfactant with agitation or sonication
c) cleaving the reverse micelle
d) extract the biomolecule
Procedure 2
a) mixing of biomolecule into a solution containing a reverse micelle with agitation or sonication.
b) cleaving the reverse micelle
c) extract the biomolecule
Procedure 3
a) mixing the biomolecule into an aqueous solution
b) then extracting the aqueous solution containing the biomolecule with a hydrocarbon or halohydrocarbon containing a reverse micelle and separating the phases.
c) cleaving the reverse micelle
d) extract the biomolecule
In another preferred embodiment, the surfactant is a disulfide of general formula A-S-S-B, which contains a hydrophobic group (A) and a hydrophilic group (B).
In another preferred embodiment, the surfactant can be cleaved in the presence of the nucleic acid or biomolecule under conditions that will not destroy the biological activity of the nucleic acid or biomolecule.
In another preferred embodiment, the surfactant could be chemically modified in the presence of the nucleic acid or biomolecule. For example, the surfactant can be polymerized after micelle formation to form a xe2x80x9cshellxe2x80x9d or cage around the nucleic acid. The surfactant could be cleaved separating the bulk of its hydrophilic and hydrophobic parts thus destroying its ability to act as a surfactant.
In yet another preferred embodiment, the possible surfactants can be neutral, negatively charged, or zwitterionic but not positively charged. Neutral surfactants include (but not restricted to) polyoxyethylene alcohol""s, polyoxyethylene isoalcohol, polyoxyethylene p-t-octyl phenol (Triton), polyoxyethylene nonylphenol, polyoxyehtylene esters of fatty acids, polyoxyethylene sorbitol esters (Tween) and lipids. Negatively charged surfactants include (but not restricted to) di-(2-ethyl-hexyl) sodium sulfosuccinate (AOT), sodium dodecylsuphate (SDS), sodium dodecylsuphonate, and sodium dodecyl-N-sarcosinate. The zwitterionic surfactant could contain anionic and cationic groups on the alpha and omega positions of a long aliphatic chain. For zwitterionic surfactants that contain both anionic and cationic groups on the alpha and omega positions of a long aliphatic chain, complex formation should be done under acidic conditions so that the surfactant can have a positive charge that will interact with the nucleic acid. The anionic portion is neutralized by being protonated and therefore interacts with the non-aqueous phase. After formation of the complexes, the complexes are extracted into an aqueous solution containing a higher pH than the pH used to form the complexes.
FIG. 1 is a graph illustrating the spectra. There are shifts in the position of both the positive and negative bands and in the position of the crossover point for the 20 xcexcL pDNA solution (W0=3.35). Spectra that are similarly shifted are broadly defined as -spectra, and are attributed to a condensed toxin of pDNA. In contrast the spectra of the 60 xcexcL pDNA solution (W0=10.05) resembles the spectra of DNA in buffer alone in respect to cross-over point. However this spectra is characterized by an increase in the intensity of the negative band (maximum at 240 nm).
A complex is described that is deliverable to a cell comprising inserting a nucleic acid or other cargo into a reverse micelle. The reverse micelle has the property to compact the nucleic acid for easier delivery. The term deliverable means that the complex is capable of being delivered as defined in this specification.
A process for forming a negatively-charged, zwitterionic, or neutral complex for delivery to a cell, comprising forming a cationic reverse micelle using amphipathic molecules. Then inserting a biologically active compound into the cationic reverse micelle.
Subsequently changing the charge of the cationic reverse micelle to a negatively-charged, zwitterionic, or neutral reverse micelle and delivering it to the cell.
The amphipathic molecule may contain a siliconxe2x80x94heteroatom bond. A heteroatom is any atom other than carbon or hydrogen. Examples of a heteroatom include oxygen, nitrogen, phosphorous and sulfer.
A biologically active compound is purified is when it is isolated from a mixture of other compounds. It is purified when its purity is increased where purity is defined as the percentage of the mixture containing the desired biologically active compound. Purification can also indicate a process where the purity of the desired compound is not increased but the other compounds within the mixture are changed. Purification also indicates the extraction of a biologic compound from one mixture or solution to another mixture or solution. This can include a process where the desired biologically active compound is moved from one solvent to another (also called extraction) or is solubilized within a solvent. A biologically active compound is a compound having the potential to react with biological components for gene therapy purposes. Pharmaceuticals, proteins, peptides, viruses, antigens, carbohydrates (and conjugates), lipids, sacharides, oligonucleotides, and nucleic acids are examples of biologically active compounds.
A surfactant refers to a compound that contains a polar group (hydrophilic) and a non-polar (hydrophobic) group on the same molecule. Cleavable surfactant refers to a surfactant in which the polar group may be separated from the nonpolar group by the removal of a chemical bond located between the two groups, or to a surfactant in which the polar or non-polar group or both may be chemically modified such that the detergent properties of the surfactant are destroyed. Cleavable also means that the surfactant is labile (able to be destroyed or that the detergent properties of the surfactant are able to be destroyed) and that its surfactant properties could be destroyed by other chemical processes than bond cleavage. A disulfide bond that is labile under physiological conditions means the disulfide bond is cleaved more rapidly than oxidized glutathione or any disulfide constructed from thiols in which one of the constituent thiols is more acidic, lower pKa, than glutathione or is activated by intramolecular attack by a free thiol. Constituent in this case means the thiols that are bonded together in the disulfide bond. The surfactant properties of a compound can be destroyed by chemical modification such as converting the polar group into a less polar group. This can be accomplished by a number of chemical modifications including (but not limited to) acylation, alkylation, elimination, reduction or oxidation, of an amine (or its salt), alcohol, diol (di-alcohol) or carboxylic acid groups, or by a multistep process in which several chemical modifications are conducted (for example oxidation of an alcohol to an aldehyde (ketone) followed by nucleophilic addition to the aldehyde (ketone) resulting in an alcohol followed by elimination of the alcohol (or a derivative of it). Reverse (inverse) micelle refers to a surfactant with an internal aqueous pool. By xe2x80x9caqueousxe2x80x9d we mean containing water, but can include buffers and salts. Non-aqueous solutions are made up of organic solvents such as hydrocarbon or halohydrocarbon. Buffers are made from a weak acid or weak base and their salts. Buffer solutions resist changes in pH when additional acid or base is added to the solution. Salts are ionic compounds that dissociate into cations and anions when dissolved in solution. Salts increase the ionic strength of a solution, and consequently decrease interactions between nucleic acids with other cations.
A reverse micelle is destroyed when the micelle no longer exists and the monophase no longer exists. A reverse micelle is destroyed when the micelle is disrupted. In a preferred embodiment the reverse micelle is destroyed by chemically modifying the surfactant so that water in oil emulsion is destroyed and the phases separate. A destructible reverse micelle is a reverse micelle that can be destroyed such that the water in oil emulsion is destroyed and the phases separate. A destructible reverse micelle can undergo a biological, chemical, or biochemical reaction such that the reverse micelle is destroyed. Biological, chemical, or biochemical reactions involve the formation or cleavage of ionic and/or covalent bonds. In a preferred embodiment the destructible reverse micelle contains a surfactant that is cleavable, destroyable, or chemically modifiable. The surfactant can be a disulfide of the general formula A-S-S-B, in which chemical group A is a hydrophobic group and chemical group B is a hydrophilic group.
The present invention also relates to a method in which a biologically active compound is delivered to a cell comprising a step in which the biologically active compound is mixed with a biologically-labile surfactant. A biologically-labile surfactant is a surfactant in which the hydrophobic moiety is cleaved from the hydrophilic moiety by cellular processes or its surfactant properties are rendered inactive within the cell, tissue or organism. Examples include surfactants that contain disulfide bonds that are labile within the cell, tissue, or organism.
A transfection reagent is a compound or compounds used in the prior art that bind(s) to or complex(es) with polynucleotides and mediates their entry into cells. The. transfection reagent also mediates the binding and internalization of polynucleotides into cells. Examples of transfection reagents include cationic liposomes and lipids, calcium phosphate precipitates, and polylysine complexes. At times, the transfection reagent has a net positive charge that binds to the polynucleotide""s negative charge. The transfection reagent mediates binding of polynucleotides to cell via its positive charge (that binds to the cell membrane""s negative charge) or via ligands that bind to receptors in the cell. For example, cationic liposomes or polylysine complexes have net positive charges that enable them to bind to DNA.
Other vehicles are also used, in the prior art, to transfer genes into cells. These include complexing the polynucleotides on particles that are then accelerated into the cell. This is termed biolistic or gun techniques. Other methods include eletroporation in which a device is used to give an electric charge to cells. The charge increases the permeability of the cell.
The term xe2x80x9cnucleic acidxe2x80x9d is a term of art that refers to a polymer containing at least two nucleotides. xe2x80x9cNucleotidesxe2x80x9d contain a sugar deoxyribose (in DNA) or ribose (in RNA), a base, and a phosphate group. Nucleotides are linked together through the phosphate groups. xe2x80x9cBasesxe2x80x9d include purines and pyrimidines, which further include natural compounds adenine, thymine, guanine, cytosine, uracil, inosine, and synthetic derivatives of purines and pyrimidines, or natural analogs. Nucleotides are the monomeric units of nucleic acid polymers. A xe2x80x9cpolynucleotidexe2x80x9d is distinguished here from an xe2x80x9coligonucleotidexe2x80x9d by containing more than 80 monomeric units; oligonucleotides contain from 2 to 80 nucleotides. The term nucleic acid includes deoxyribonucleic acid (xe2x80x9cDNAxe2x80x9d) and ribonucleic acid (xe2x80x9cRNAxe2x80x9d). DNA may be in the form of anti-sense, plasmid DNA, parts of a plasmid DNA, vectors (P1, PAC, BAC, YAC, artificial chromosomes), expression cassettes, chimeric sequences, chromosomal DNA, or derivatives of these groups. RNA may be in the form of oligonucleotide RNA, tRNA (transfer RNA), snRNA (small nuclear RNA), rRNA (ribosomal RNA), mRNA (messenger RNA), anti-sense RNA, ribozymes, chimeric sequences, or derivatives of these groups. xe2x80x9cAnti-sensexe2x80x9d is a nucleic acid that interferes with the function of DNA and/or RNA. This may result in suppression of expression. Natural nucleic acids have a phosphate backbone, artificial nucleic acids may contain other. types of backbones, nucleotides, or bases. These include PNAs (peptide nucleic acids), phosphothionates, and other variants of the phosphate backbone of native nucleic acids. In addition, DNA and RNA may be single, double, triple, or quadruple stranded. xe2x80x9cExpression cassettexe2x80x9d refers to a natural or recombinantly produced nucleic acid which is capable of expressing protein(s). A DNA expression cassette typically includes a promoter (allowing transcription initiation), and a sequence encoding one or more proteins. Optionally, the expression cassette may include transcriptional enhancers, non-coding sequences, splicing signals, transcription termination signals, and polyadenylation signals. An RNA expression cassette typically includes a translation initiation codon (allowing translation initiation), and a sequence encoding one or more proteins. Optionally, the expression cassette may include translation termination signals, a polyadenosine sequence, internal ribosome entry sites (IRES), and non-coding sequences.
Delivery of a nucleic acid means to transfer a nucleic acid from a container outside a mammal to near or within the outer cell membrane of a cell in the mammal. The term xe2x80x9ctransfectionxe2x80x9d may be used, in general, as a substitute for the term xe2x80x9cdelivery,xe2x80x9d or, more specifically, the transfer of a nucleic acid from directly outside a cell membrane to within the cell membrane. The transferred (or xe2x80x9ctransfectedxe2x80x9d) nucleic acid may contain an expression cassette. If the nucleic acid is a primary RNA transcript that is processed into messenger RNA, a ribosome translates the messenger RNA to produce a protein within the cytoplasm. If the nucleic acid is a DNA, it enters the nucleus where it is transcribed into a messenger RNA that is transported into the cytoplasm where it is translated into a protein. Therefore if a nucleic acid expresses its cognate protein, then it must have entered a cell. A protein may subsequently be degraded into peptides, which may be presented to the immune system.
Polypeptide refers to a linear series of amino acid residues connected to one another by peptide bonds between the alpha-amino group and carboxyl group of contiguous amino acid residues.
xe2x80x9cProteinxe2x80x9d refers herein to a linear series of greater than 2 amino acid residues connected one to another as in a polypeptide. A xe2x80x9ctherapeuticxe2x80x9d effect of the protein in. attenuating or preventing the disease state can be accomplished by the protein either staying within the cell, remaining attached to the cell in the membrane, or being secreted and dissociated from the cell where it can enter the general circulation and blood. Secreted proteins that can be therapeutic include hormones, cytokines, growth factors, clotting factors, anti-protease proteins (e.g., alphal-antitrypsin), angiogenie proteins (e.g., vascular endothelial growth factor, fibroblast growth factors), anti-angiogenic proteins (e.g., endostatin, angiostatin), and other proteins that are present in the blood. Proteins on the membrane can have a therapeutic effect by providing a receptor for the cell to take up a protein or lipoprotein (e.g., low density lipoprotein receptor). Therapeutic proteins that stay within the cell (xe2x80x9cintracellular proteinsxe2x80x9d) can be enzymes that clear a circulating toxic metabolite as in phenylketonuria. They can also cause a cancer cell to be less proliferative or cancerous (e.g., less metastatic), or interfere with the replication of a virus. Intracellular proteins can be part of the cytoskeleton (e.g., actin, dystrophin, myosins, sarcoglycans, dystroglycans) and thus have a therapeutic effect in cardiomyopathies and musculoskeletal diseases (e.g., Duchenne muscular dystrophy, limb-girdle disease). Other therapeutic proteins of particular interest to treating heart disease include polypeptides affecting cardiac contractility (e.g., calcium and sodium channels), inhibitors of restenosis (e.g., nitric oxide synthetase), angiogenic factors, and anti-angiogenic factors.
Biomolecule refers to peptides, polypeptides, proteins, enzymes, polynucleotides, oligonucleotides, viruses, antigens, carbohydrates (and congugates), lipids, and sacharides.
Enzymes are proteins evolved by the cells of living organisms for the specific function of catalyzing chemical reactions.
A chemical reaction can take place within the micelle and nucleic acid complex. A chemical reaction is defined as the formation or cleavage of covalent or ionic bonds. As a result of the chemical reaction a polymer can be formed. A polymer is defined as a compound containing more than two monomers. A monomer is a compound that can be attached to itself or another monomer and thus form a polymer. In one preferred embodiment the surfactant is polymerized by chain or step polymerization and then the. surfactant properties are destroyed. This destruction of the surfactant properties could be a accomplished by breaking a chemical bond and separating the hydrophilic and hydrophobic moieties.
A chemical reaction can be used to attach a gene transfer enhancing signal to the nucleic acid complex. The gene transfer enhancing signal (or abbreviated as the Signal) is defined in this specification as a molecule that modifies the nucleic acid complex and can direct it or the nucleic acid to a cell location (such as tissue) or location in a cell (such as the nucleus) either in culture or in a whole organism. By modifying the cellular or tissue location of the foreign gene, the expression of the foreign gene can be enhanced.
The gene transfer enhancing signal can be a protein, peptide, lipid, steroid, sugar, carbohydrate, (non-expressing) nucleic acid or synthetic compound. The gene transfer enhancing signals enhance cellular binding to receptors, cytoplasmic transport to the nucleus and nuclear entry or release from endosomes or other intracellular vesicles.
Nuclear localizing signals enhance the targeting of the gene into proximity of the nucleus and/or its entry into the nucleus. Such nuclear transport signals can be a protein or a peptide such as the SV40 large T ag NLS or the nucleoplasmin NLS. These nuclear localizing signals interact with a variety of nuclear transport factors such as the NLS receptor (karyopherin alpha) which then interacts with karyopherin beta. The nuclear transport proteins themselves could also function as NLS""s since they are targeted to the nuclear pore and nucleus.
Signals that enhance release from intracellular compartments (releasing signals) can cause DNA release from intracellular compartments such as endosomes (early and late), lysosomes, phagosomes, vesicle, endoplasmic reticulum, golgi apparatus, trans golgi network (TGN), and sarcoplasmic reticulum. Release includes movement out of an intracellular compartment into cytoplasm or into an organelle such as the nucleus. Releasing signals include chemicals such as chloroquine, bafilomycin or Brefeldin A1. and the ER-retaining signal (KDEL sequence), viral components such as influenza virus hemagglutinin subunit HA-2 peptides and other types of amphipathic peptides.
Cellular receptor signals are any signal that enhances the association of the gene with a cell. This can be accomplished by either increasing the binding of the gene to the cell surface and/or its association with an intracellular compartment, for example: ligands that enhance endocytosis by enhancing binding the cell surface. This includes agents that target to the asialoglycoprotein receptor by using asiologlycoproteins or galactose residues. Other proteins such as insulin, EGF, or transferrin can be used for targeting. Peptides that include the RGD sequence can be used to target many cells. Chemical groups that react with sulfhydryl or disulfide groups on cells can also be used to target many types of cells. Folate and other vitamins can also be used for targeting. Other targeting groups include molecules that interact with membranes such as lipids fatty acids, cholesterol, dansyl compounds, and amphotericin derivatives. In addition viral proteins could be used to bind cells.
A polynucleotide can be delivered to a cell in order to produce a cellular change that is therapeutic. The delivery of polynucleotides or other genetic material for therapeutic purposes (the art of improving health in an animal including treatment or prevention of disease) is gene therapy. The polynucleotides are coded to express a whole or partial protein, or may be anti-sense, and can be delivered either directly to the organism in situ or indirectly by transfer to a cell that is then transplanted into the organism. The protein can be missing or defective in an organism as a result of genetic, inherited or acquired defect in its genome. For example, a polynucleotide may be coded to express the protein dystrophin that is missing or defective in Duchenne muscular dystrophy. The coded polynucleotide is delivered to a selected group or groups of cells and incorporated into those cell""s genome or remain apart from the cell""s genome. Subsequently, dystrophin is produced by the formerly deficient cells. Other examples of imperfect protein production that can be treated with gene therapy include the addition of the protein clotting factors that are missing in the hemophilia""s and enzymes that are defective in inborn errors of metabolism such as phenylalanine hydroxylase. A delivered polynucleotide can also be therapeutic in acquired disorders such as neurodegenerative disorders, cancer, heart disease, and infections. The polynucleotide. has its therapeutic effect by entering the cell. Entry into the cell is required for the polynucleotide to produce the therapeutic protein, to block the production of a protein, or to decrease the amount of a RNA.
A therapeutic effect of the protein in attenuating or preventing the disease state can be accomplished by the protein either staying within the cell, remaining attached to the cell in the membrane or being secreted and dissociating from the cell where it can enter the general circulation and blood. Secreted proteins that can be therapeutic include hormones, cytokines, growth factors, clotting factors, anti-protease proteins (e.g. alpha-antitrypsin) and other proteins that are present in the blood. Proteins on the membrane can have a therapeutic effect by providing a receptor for the cell to take up a protein or lipoprotein. For example, the low density lipoprotein (LDL) receptor could be expressed in hepatocytes and lower blood cholesterol levels and thereby prevent atherosclerotic lesions that can cause strokes or myocardial infarction. Therapeutic proteins that stay within the cell can be enzymes that clear a circulating toxic metabolite as in phenylketonuria. They can also cause a cancer cell to be less proliferative or cancerous (e.g. less metastatic). A protein within a cell could also interfere with the replication of a virus.
The delivered polynucleotide can stay within the cytoplasm or nucleus apart from the endogenous genetic material. Alternatively, the polynucleotide could recombine (become a part of) the endogenous genetic material. For example, DNA can insert into chromosomal DNA by either homologous or non-homologous recombination.
Parenchymal cells are the distinguishing cells of a gland or organ contained in and supported by the connective tissue framework. The parenchymal cells typically perform a function that is unique to the particular organ. The term xe2x80x9cparenchymalxe2x80x9d often excludes cells that are common to many organs and tissues such as fibroblasts and endothelial cells within the blood vessels. In a liver organ, the parenchymal cells include hepatocytes, Kupffer cells and the epithelial cells that line the biliary tract and bile ductules. The major constituent of the liver parenchyma are polyhedral hepatocytes (also known as hepatic cells) that presents at least one side to an hepatic sinusoid and apposed sides to a bile canaliculus. Liver cells that are not parenchymal. cells include cells within the blood vessels such as the endothelial cells or fibroblast cells.
In striated muscle, the parenchymal cells include myoblasts, satellite cells, myotubules, and myofibers. In cardiac muscle, the parenchymal cells include the myocardium also known as cardiac muscle fibers or cardiac muscle cells and the cells of the impulse connecting system such as those that constitute the sinoatrial node, atrioventricular node, and atrioventricular bundle. In a pancreas, the parenchymal cells include cells within the acini such as zymogenic cells, centroacinar cells, and basal or basket cells and cells within the islets of Langerhans such as alpha and beta cells. In spleen, thymus, lymph nodes and bone marrow, the parenchymal cells include reticular cells and blood cells (or precursors to blood cells) such as lymphocytes, monocytes, plasma cells and macrophages.
In the nervous system which includes the central nervous system (the brain and spinal cord) peripheral nerves, and ganglia, the parenchymal cells include neurons, glial cells, microglial cells, oligodendrocytes, Schwann cells, and epithelial cells of the choroid plexus. In the kidney, parenchymal cells include cells of collecting tubules and the proximal and distal tubular cells. In the prostate, the parenchyma includes epithelial cells. In glandular tissues and organs, the parenchymal cells include cells that produce hormones. In the parathyroid glands, the parenchymal cells include the principal cells (chief cells) and oxyphilic cells. In the thyroid gland, the parenchymal cells include follicular epithelial cells and parafollicular cells. In the adrenal glands, the parenchymal cells include the epithelial cells within the adrenal cortex and the polyhedral cells within the adrenal medulla. In the parenchyma of the gastrointestinal tract such as the esophagus, stomach, and intestines, the parenchymal cells include epithelial cells, glandular cells, basal, and goblet cells. In the parenchyma of lung, the parenchymal cells include the epithelial cells, mucus cells, goblet cells, and alveolar cells. In fat tissue, the parenchymal cells include adipose cells or adipocytes. In the skin, the parenchymal cells include the epithelial cells of the epidermis, melanocytes, cells of the sweat glands, and cells of the hair root. In cartilage, the parenchyma includes chondrocytes. In bone, the parenchyma includes osteoblasts, osteocytes, and osteoclasts. Intravascular refers to an intravascular route of administration that enables a polymer, oligonucleotide, or polynucleotide to be delivered to cells more evenly distributed and more efficiently than direct injections. Intravascular herein means within an internal tubular structure called a vessel that is connected to a tissue or organ within the body of an animal, including mammals. Within the cavity of the tubular structure, a bodily fluid flows to or from the body part. Examples of bodily fluid include blood, lymphatic fluid, or bile. Examples of vessels include arteries, arterioles, capillaries, venules, sinusoids, veins, lymphatics, and bile ducts. The intravascular route includes delivery through the blood vessels such as an artery or a vein. xe2x80x9cIntracoronaryxe2x80x9d refers to an intravascular route for delivery to the heart wherein the blood vessels are the coronary arteries and veins.
Permeability is defined herein as the propensity for macromolecules such as nucleic acids to move through vessel walls and enter the extravascular space. One measure of permeability is the rate at which macromolecules move through the vessel wall and out of the vessel. Another measure of permeability is the lack of force that resists the movement through the vessel wall and out of the vessel. Vessels contain elements that prevent macromolecules from leaving the intravascular space (internal cavity of the vessel). These elements include endothelial cells and connective material (e.g., collagen). High permeability indicates that there are fewer of these elements that can block the egress of macromolecules and that the spaces between these elements are larger and more numerous. In this context, high permeability enables a high percentage of nucleic acids being delivered to leave the intravascular space, while low permeability indicates that a low percentage of the nucleic acids will leave the intravascular space.
The permeability of a blood vessel can be increased by increasing the intravascular hydrostatic pressure. In a preferred embodiment, the intravascular hydrostatic pressure is increased by rapidly (from 1 seconds to 30 minutes) injecting a nucleic acid in solution into the blood vessel, which increases the hydrostatic pressure. In another preferred embodiment, hydrostatic pressure is increased by obstructing the outflow of the injection solution from the tissue for a period of time sufficient to allow delivery of a nucleic acid. Obstructing means to block or impede the outflow of injection fluid, thereby transiently (reversibly) blocking the outflow of the blood. Furthermore, rapid. injection may be combined with obstructing the outflow in yet another preferred embodiment. For example, an afferent vessel supplying an organ is rapidly injected while the efferent vessel draining the tissue is blocked transiently (e.g., by ligation, or by an inflated intravascular balloon). The efferent vessel (also called the venous outflow or tract) draining outflow from the tissue is partially or totally clamped for a period of time sufficient to allow delivery of a nucleic acid. In the reverse, an efferent vessel is injected while the corresponding afferent vessel is occluded.
An administration route involving the mucosal membranes is meant to include nasal, bronchial, inhalation into the lungs, or via the eyes.
Transdermal refers to application to mammal skin in which drug delivery occurs by crossing the dermal layer.
Crosslinking refers to the chemical attachment of two or more molecules with a bifunctional reagent. A bifunctional reagent is a molecule with two reactive ends. The reactive ends can be identical as in a homobifunctional molecule, or different as in a heterobifucnctional molecule.
Electrostatic interactions are the non-covalent association of two or more substances due to attractive forces between positive and negative charges.
Amphipathic compounds have both hydrophilic (water-soluble) and hydrophobic (water-insoluble) parts.
A polycation is a polymer containing a net positive charge, for example poly-L-lysine hydrobromide. The polycation can contain monomer units that are charge positive, charge neutral, or charge negative, however, the net charge of the polymer must be positive. A polycation also can mean a non-polymeric molecule which contains two or more positive charges. A polyanion is a polymer containing a net negative charge, for example polyglutamic acid. The polyanion can contain monomer units that are charge negative, charge neutral, or charge positive, however, the net charge on the polymer must be negative. A polyanion can also mean a non-polymeric molecule that contains. two or more negative charges. The term polyion includes polycation, polyanion, zwitterionic polymers, and neutral polymers. The term zwitterionic refers to the product (salt) of the reaction between an acidic group and a basic group that are part of the same molecule.
Mixing means the method of interdispursing two or more solvents, or solvent(s) and solute(s). Sonication and agitation are forms of mixing. Solvent refers to a material in the liquid phase that can be used to solubilize (dissolve) a compound. Solute refers to a compound dissolved in a solvent.
Hydrocarbon means containing carbon and hydrogen atoms; and halohydrocarbon means containing carbon, halogen (F, Cl, Br, I), and hydrogen atoms.
Alkyl means containing sp3 hybridized carbon atoms; alkenyl means containing two or more sp2 hybridized carbon atoms; aklkynyl means containing two or more sp hybridized carbon atoms; aralkyl means containing one or more aromatic ring(s) in addition containing sp3 hybridized carbon atoms; aralkenyl means containing one or more aromatic ring(s) in addition to containing two or more sp2 hybridized carbon atoms; aralkynyl means containing one or more aromatic ring(s) in addition to containing two or more sp hybridized carbon atoms; steroid includes natural and unnatural steroids and steroid derivatives. A steroid derivative means a sterol, a sterol in which the hydroxyl moiety has been modified (for example, acylated), or a steroid hormone, or an analog thereof; carbohydrates include natural and unnatural sugars (for example glucose), and sugar derivatives (a sugar derivative means a system in which one or more of the hydroxyl groups on the sugar moiety has been modified (for example acylated), or a system in which one or more of the hydroxyl groups is not present); polyoxyethylene means a polymer having two to six (n=2-6) ethylene oxide units (xe2x80x94(CH2CH2O)nxe2x80x94) or a derivative thereof; and R not identified by number is meant to be any compatible group, for example alkyl, alkenyl, alkynyl, aralkyl, aralkenyl, or aralkynyl, and can include heteroatoms (N, O, S), and carbonyl groups.
Hydrophilic groups indicate in qualitative terms that the chemical moiety is water-preferring. Typically, such chemical groups are water soluble, and are hydrogen bond donors or acceptors with water. Examples of hydrophilic groups include compounds with the following chemical moieties carbohydrates; polyoxyethylene, peptides, oligonucleotides and groups containing amines, amides, alkoxy amides, carboxylic acids, sulfurs, or hydroxyls. Hydrophobic groups indicate in qualitative terms that the chemical moiety is water-avoiding. Typically, such chemical groups are not water soluble, and tend not to hydrogen bond. Hydrocarbons are hydrophobic groups.
The terms xe2x80x9ctherapeuticxe2x80x9d and xe2x80x9ctherapeutic resultsxe2x80x9d are defined in this application as levels of gene products, including reporter (marker) gene products, which indicate a reasonable expectation of gene expression using similar compounds (other nucleic acids including other genes), at levels considered sufficient by a person having ordinary skill in the art of gene therapy. For example: Hemophilia A and B are caused by deficiencies of the X-linked clotting factors VIII and IX, respectively. Their clinical course is greatly influenced by the percentage of normal serum levels of factor VIII or IX:  less than 2%, severe; 2-5%, moderate; and 5-30% mild. This indicates that in severe patients only 2% of the normal level can be considered therapeutic. Levels greater than 6% prevent spontaneous bleeds but not those secondary to surgery or injury. A person having ordinary skill in the art of gene therapy would reasonably anticipate therapeutic levels of expression of a gene specific for a disease based upon sufficient levels of marker gene results. In the Hemophilia example, if marker genes were expressed to yield a protein at a level comparable in volume to 2% of the normal level of factor VIII, it can be reasonably expected that the gene coding for factor VIII would also be expressed at similar levels.
There are three types of reporter (marker) gene products that are expressed from reporter genes. The reporter gene/protein systems include:
a) Intracellular gene products such as luciferase, xcex2-galactosidase, or chloramphenicol acetyl transferase. Typically, they are enzymes whose enzymatic activity can be easily measured.
b) Intracellular gene products such as xcex2-galactosidase or green fluorescent protein which identify cells expressing the reporter gene. On the basis of the intensity of cellular staining, these reporter gene products also yield qualitative information concerning the amount of foreign protein produced per cell.
Secreted gene products such as growth hormone, factor IX, or alphal-antitrypsin are useful for determining the amount of a secreted protein that a gene transfer procedure can produce. The reporter gene product can be assayed in a small amount of blood.